The long range purpose of this project is to develop a better understanding of environmental effects on gene frequency distributions. The work is conducted in collaboration with scientists in the Laboratory of Environmental Mutagenesis. Current research topics are: 1) the relation between the frequency environments on the progress of natural selection; 3) an assessment of the accuracy of existing models for predicting the transient behavior of recessive lethal alleles; 4) theoretical developments in stochastic differential equations applicable to problems in population genetics. BIBLIOGRAPHIC REFERENCE: Crump, K.S. and Gillespie, J.H.: The dispersion of a neutral allele considered as a branching process. J. Appl. Prob. 13, 208-218, 1976.